Fixed issue with selecting Instagram images.

Based on the log files, it appears that Instagram changed their auth flow and are now using some endpoints from Facebook. I was able to fix it by adding the following urls to the allowedUrlPrefix.plist:
https://s-static.ak.facebook.com/connect/xd_arbiter/
https://www.facebook.com/connect/ping

related issue: https://github.com/Ink/ios-picker/issues/56